Cardiac monitoring is often recommended for patients with palpitations, those with syncope, and those whose medication changes or whose electrocardiogram indicates dysrhythmia. Tachyarrhythmias are most often treated with medications, however, one prominent side effect of their usage is the possibility of induction of bradycardia. Another possible side effect that can result from the use of these medications is prolongation of the QT interval, which can lead to torsade de pointes and which may be life-threatening. Short-term monitoring often takes the form of hospitalization and telemetry observation, or alternatively, outpatient monitoring for 24 hours or longer periods such as might be feasible with a loop recorder.
The physician is often forced to make a judgment as to the likelihood of a symptomatic bradycardia requiring pacing on a temporary basis. If home monitoring is selected, any significant, symptomatic bradycardia is recorded but not treated, and therefore, a bradycardic episode possibly may be documented without the ability to administer timely therapy.
Selection of hospitalization for observation allows fast treatment of an identified bradycardia or in the case of prolonged QT interval, torsade de pointes. Such treatment may include withdrawal of any offending agent, in the case of bradycardia treatment with atropine, and in the case of either bradycardia or torsade, temporary external or internal pacing. To err on the side of hospitalization drives up cost and inconvenience for a large number of patients with the actual bradycardia therapy or therapy for torsade being administered to relatively few. To err on the side of outpatient monitoring without the ability to treat a recorded bradyarrhythmia or torsade risks the life of the patient. Further, even longer term monitoring for suspected dysrhythmias such as transtelephonic monitoring systems or the Medtronic Reveal system or newer injectable loop recorders risks the bradycardic rhythm not being treated in a timely fashion sufficient to prevent patient injury.
Many situations such as bundle branch block, prolonged, symptomatic HV, fractionated His bundles, tachy-brady, Wenckebach heart block, and medication initiation or escalation raise suspicion for bradycardia or torsade that may require pacing. The decision of whether to pace a patient is often a judgment call because only after a symptomatic bradycardic event is revealed is the patient a definite pacemaker candidate. Unfortunately, once a sufficient event has occurred the patient may have already been injured. However, to offer a pacemaker before sufficient event increases the cost, patient doubt, and physician scrutiny.
Current bradycardia management is typically divided into a diagnostic arm and a therapeutic arm. The implications are that only after the bradycardia has been determined on a monitor is the patient a candidate for permanent pacing. Indications for permanent pacing are in a constant revision to balance between preventing too many pacemaker implantations in those who do not need them, but to allow those with sufficient evidence to suggest that they may need one to obtain one prior to a catastrophic event. These indications are based on statistic likelihoods of symptomatic bradycardic rhythms, but are not sufficiently patient specific or predictive to ensure that the correct decision is made. Thus, some patients receive pacemakers, but never truly require them, while other patients do not technically qualify for a pacemaker under current indications, but subsequently have an event that was suspected but was not treated by pacing at the time it occurred.
Although external pacing systems exist, their usage has been exclusively to treat bradycardia in hospitalized patients. An external pacing system for outpatient use is not known to exist.
What is needed is a device that is not cumbersomely large and that can sense bradycardia, treat in real time with external pacing, record the dysrhythmia, and transmit it to a health care professional. A further need exists for a device that can sense prolongation of the QT interval in patients that are subject to initiation or escalation of antiarrhythmic therapy and deliver pacing to overdrive suppressed potential torsade de pointes, and therefore, prevent injury or death in those patients as well.